In-circuit test (ICT) may include testing a populated printed circuit board (PCB) to determine whether the PCB was properly assembled. For example, in-circuit testing may include performing tests to identify, on the PCB, short circuits, open circuits, wrong value components, unexpected resistance, capacitance, or inductance, and so forth. A test fixture acts as an interface between the PCB and test equipment used to perform in-circuit testing.
ICT operates by gaining electrical access to a PCB test through the test fixture. When performing electrical tests, each active and passive component is typically isolated from other surrounding components and tested on an individual basis. The PCB under test is designed to support this level of testability by incorporating test pads on signal nets that can be contacted by the test fixture.
The test fixture typically provides the physical and electrical interface between an ICT system and a unit under test (UUT), such as a PCB, as described above. One of the purposes of the test fixture is to translate, geographically, test pins of a test system's receiver interface to test pad locations on the UUT. This routing of electrical signals from the test system's receiver to the UUT test pads has historically been performed using interconnect methods within the test fixture. Perhaps the most widely used interconnect method in an ICT fixture includes direct wiring from a pin connecting to the tester to a POGO pin that contacts the test pad on the UUT. This type of test fixture is called a “wired fixture”. Wired fixtures are generally considered to be lower cost fixtures, especially in one-off situations or in low volume usage.
Another type of interconnect method in an ICT fixture includes use of a PCB to route signals, rather than the individual wires as in a wired fixture. The type of test fixture that uses a PCB to route signals is called a “wireless fixture”. Wireless fixtures are generally more expensive to manufacture than wired fixtures and are usually deployed only in higher-volume applications, where the price of designing and building a PCB can be amortized over multiple test fixtures.
Both of the foregoing types of test fixtures have a number of common drawbacks in that the time to develop the fixtures may be too long (e.g., on the order of three to eight weeks, depending upon node count and complexity), and that the cost may be higher than the market is willing to bear for a disposable buy item.
In this regard, one of the issues with ICT is the cost and development time associated with the test fixture. These test fixtures, whose cost can range from $10,000 to over $100,000, are typically unique to the specific board being tested and cannot be used to test any other board types. As a result, while the manufacturer may have only one or two ICT systems on a manufacturing line, it is likely the manufacturer has purchased tens to hundreds of different test fixtures, many of which have become obsolete as a result of short product lifetimes.